# What is Lr circuit: Definition and 30 Discussions

A resistor–inductor circuit (RL circuit), or RL filter or RL network, is an electric circuit composed of resistors and inductors driven by a voltage or current source. A first-order RL circuit is composed of one resistor and one inductor and is the simplest type of RL circuit.
A first order RL circuit is one of the simplest analogue infinite impulse response electronic filters. It consists of a resistor and an inductor, either in series driven by a voltage source or in parallel driven by a current source.

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1. ### Solving Equation to Analyze Steady State Current

I set up the equation ##V-iR-L\frac{di}{dt}=0##, with ##i(0)## and by solving it I got ##i(t)=\frac{V}{R}(1-e^{-\frac{R}{L}t})##. Then, since the steady state current is ##i_s=\frac{V}{R}## I imposed the condition ##i(t_1)=\frac{9}{10}\frac{V}{R}\Leftrightarrow...
2. ### Engineering Finding Time Constant T Without L for an LR Circuit

Edit: Picture of the Circuit (Simple RL circuit) The value of L is not given. Attempt to Solve for T by Rearranging Equation 1: I rearranged the equation to solve for T, using Ohm's Law so solve for I = V/R at each time. https://www.desmos.com/calculator/qlb2n6w4bg This graph is...

4. ### LR Circuit Analysis: Solving Equations w/ Kirchhoff's Rule

Above is the figure of the question. According to Kirchhoff's Rule, I have obtained three equations $$\varepsilon-iR_{10}-L_{40}\frac{di_1}{dt}=0$$ $$L_{40}\frac{di_1}{dt}-i_2R_{60}=0$$ $$i_2R_{60}-R_{30}(i-i_1-i_2)-L_{15}\frac{d(i-i_1-i_2)}{dt}=0,$$ where ##\varepsilon## stands for emf=100V...
5. ### LR circuit - Which bulb gets dim quickly?

Homework Statement Homework EquationsThe Attempt at a Solution When the switch is off , the current in the inductor doesn't drop to zero instantaneously . The current in the loop consisting of inductor , resistor and two bulbs will decay gradually . Now since there is a complete circuit...
6. ### I RL vs LR Circuits: Low-Pass/High-Pass Filters Explained

Is there any difference between RL vs LR circuit? Which one is for low-pass/high-pass filter? Please help
7. S

### Maximum rate at which energy is stored in a LR circuit

Homework Statement An Inductor L and a Resistance R are connected in series with a battery of emf E. Find the maximum rate at which the energy is stored in the magnetic field. Homework Equations Energy stored in an inductor : U= 1/2Li2 For a simple LR circuit with a DC voltage source the...
8. ### Voltage across switch in LR circuit as switch is opened?

1. I thought that when switch was closed, voltage at the right side of switch was 0 and long time after the switch is open, the voltage at the right side of the switch becomes 0. 2. After the switch is open ecause of the inductor, voltage at the right side of the switch is εL = induced emf So...
9. ### Engineering Circuit analyse -- LR circuit frequency response

Homework Statement Find X [/B] Homework Equations V1(t)=8cos(12000t) V0(t)=Xcos(12000t+θ) The Attempt at a Solution [/B] I've tried quiet a lot actually, but all in vain. Seems like I am either misunderstanding something, or i am just too tired to think at the moment. Either way, I am...
10. ### LC Circuit Problem Homework: Calculate Values of L & R

Homework Statement When the current in the portion of the circuit shown in the figure below is 4.00 A and increases at a rate of 0.500 A/s, the measured voltage is ∆ = 15.0 V. When the current is 4.00 A and decreases at the rate of 0.500 A/s, the measured voltage is ∆ = 10.0 V. Calculate the...
11. ### LR circuit in parallel, need someone to check answer

Homework Statement L is a perfect inductor with inductance L. The switch is turned on at t=0 and the currents i1 and i2 run trhough the circuit as indicated by the figure. Homework Equations Given this circuit I need to find i1 and i2 for t=0 and t => infinity. The Attempt at a Solution For...
12. ### What is the voltage across an inductor in an LR circuit?

Homework Statement An inductor is connected to the terminals of a battery that has an emf of 12.0Vand negligible internal resistance. The current is 4.86mA at 0.940ms after the connection is completed. After a long time the current is 6.45mA. Homework Equations V = IR V(t) = V0 (exp(-t/τ))...
13. ### How Does Frequency Affect RLC Circuit Outputs?

Homework Statement In each of the four circuits shown, an AC input voltage, ##V_0 cos(\omega t)## is applied on the left and the output voltage is measured on the right. Treat the input frequency as a...
14. ### LR Circuit Analysis: Find Current i When Switch is Opened

Homework Statement Switch S is closed for long time in the figure shown. Find the current i as soon as the switch is opened. The Attempt at a Solution At t=∞ inductor behaves as closed circuit. So, I can simply replace it with a wire and calculate the current which comes out to be 9A...
15. ### LR Circuit Analysis: Calculating Current and Gradient (0-0.6 seconds)

A coil connected across a d.c. supply will cause a spark to occur across a switch when turned off. The current flowing in the circuit at this moment is given by the equation i = IetR/L amps. Where I is the maximum circuit current, R the resistance of the coil and L the inductance of the coil...
16. ### Find the voltage of an inductor in an LR circuit

Homework Statement at t=0 switch S is closed. Just after the switch is closed what are i1, i2, the potential difference across V2 across resistor 2, and Vl across the inductor? A long time after the switch is closed, what are i1, i2, V2, and Vl? Emf = 12V, R1= 15 ohms, R2 = 25 ohms, and L...
17. ### RC discharge into an LR circuit

Hello, I am working on a creating the characteristic equation (in general terms) of the voltage (and current, but not as important) for the capacitor in a RC connected to a LR. The RC circuit is initially charge (say has been connected to a power supply for all time before t = 0) and at t = 0 a...
18. ### LR Circuit with resistors in parallel

Homework Statement Homework Equations V = IR I = V/R (1 - e^(-t / τ)) τ = L / R The Attempt at a Solution I'm so thrown off by these two problems. Every example I have done has nothing in parallel and it is simple, but my homework question involves having to do a...
19. ### LR Circuit: Book Mistake or Misunderstanding?

problem: switch of LR circuit is closed at time = 0; what is ratio of inductor's self-induced emf ( E(L) ) to battery's emf ( E(bat) ) at t = 2τ? my solution: switch is closed so current begins to build up according to equation: i = (E(bat)/R) (1-e^(-t/τ) ) multiplying R on both sides and...
20. ### Energy stored in an inductor of an LR circuit

Homework Statement An LR circuit has a resistance R = 25 Ω, an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved? Homework Equations \epsilon= -d\phim/dt=-L\frac{dI}{dt} Um=\frac{1}{2}LI2...
21. ### LR Circuit Data Logging: Measuring Frequency Changes with Inductance Variations

Heya Everyone I decided to do some experiment with an LR circuit. I have an inductor in series with a resistor connected to a function generator. I will set the frequency to the resonant frequency of the circuit. Now, I will change the inductance of the inductor by bringing in a conductor...
22. ### LR Circuit: Solving for Charge Flow?

I solved it :pHomework Statement The Attempt at a Solution I need help with part (a) Current in LR circuit, i = i_o (1 - e^{-t/\tau}) and \tau = \frac{L}{R} so, \frac{dq}{dt} = i_0 (1 - e^{-t/\tau}) integrating it is not giving me the correct answer.
23. ### Di/dt for Growth and Decay in LR Circuit

Why is the emf induced in an inductor much larger when the switch connecting it to a battery is closed than when the switch is opened? Somewhere in a text I had read that di/dt is very large when an LR circuit breaks but then its value for growth and decay in an LR circuit is...
24. ### Finding Max Current in an LR Circuit

Homework Statement An LR circuit consists of an inductor with L = 2.3 × 10-4 H and a resistor with R = 1.10 Ω connected in series to an oscillating source of emf. This source generates a voltage ε = εmaxsin( ωt) with εmax = 0.80 V and ω = 6.00 × 104 rad/s. What is the maximum current in...
25. ### LR circuit, energy dissipated?

http://img527.imageshack.us/img527/1787/lccircuitrk6.th.gif The switch S is closed for a long time and then released again. How much energy is dissipated through the resistors after the switch is released? It should be (LI^2)/2 shouldn't it? Where I is the current right before the...
26. ### Solve LR Circuit Problem: Find New Values for R & Vo

Homework Statement If You want to turn on the current through a coil of self inductance L in a controlled manner, so you place it in series with a resistor R= 2200 ohm, a switch, and a dc voltage source Vo=240 V. After closing the switch, you find that the current through the coil builds up to...
27. ### Calculating Low-Pass Filter Corner Frequency for LR Circuit

Homework Statement Show that a series LR circuit is a Low Pass filter if the output is taken across the resistor. Calculate the corner frequency, f_c, if L = 2mH and R = 10k\Omega. Homework Equations H(\omega)\,=\,\frac{V_0(t)}{V_i(t)} H\left(\omega_c\right)\,=\,\frac{1}{\sqrt{2}}...
28. ### Engineering Solving Series LR Circuit: Calculate Wattless & Power Components

Homework Statement 1)A coil of self inductance of 0.7 Henry is joined in series with a non inductive resistance of 5 ohms. Calculate the wattless and power components as well as total current when connected to a supply of 200 volts at frequency of 50 cycles per second. Homework Equations...
29. ### Phase difference in CR and LR circuit

I have just done an experiment on CR and LR circuits. http://img9.picsplace.to/img9/21/RC.jpg Connect channel 1 of the CRO across both the capacitor and resistor and channel 2 across the resistor.The trace on channel 1 is taken as the p.d. across the capacitor and that on channel 2 as ths...
30. ### How Does Energy Dissipate in an LR Circuit with a 10V Battery?

Homework Statement A LR circuit has a 10V battery, 5.50H inductor, and a 6.7 Ohm resistor. The battery is closed at t=0. (a) What is the time constant of the circuit? (b) How much energy is delivered by the battery during the first 2 seconds? (c) How much of this energy is stored in the...